裝置對裝置通訊已成為下一代行動通訊不可或缺的一部份，而同儕發現為實現裝置對裝置通訊的關鍵技術。許多文獻提出各種方法，以提升直接式同儕發現的效率，所謂直接式，即不需藉助基地台之協助。這些方法的主要概念，大都是避免在同儕發現週期中，發生不必要的訊號碰撞。然而此類方法的效能，通常會受限於裝置對裝置同儕發現的有限資源。反觀我們的方法，旨在強化同儕發現訊號抗碰撞之能力。我們提出的循環式碼塊展頻直接同儕發現法，將同儕發現之訊號延展在多個時槽上，既不用擴展頻寬，也不需重新設計訊號，只要些微修改規格書制定的規格即可。模擬和分析的結果顯示出，採用循環式碼塊展頻直接同儕發現法，可有效降低碰撞率和故障機率。

Device-to-device (D2D) communications has become a pivotal piece to complete the puzzle of future generation of wireless communication systems. The enabling technol- ogy for the D2D communications lies in its discovery mechanism. Plenty of works have been proposed to enhance the efficiency of direct D2D discovery without network assis- tance. Generally, the main idea of these works is to avoid unnecessary collisions during the discovery period. However, owing to the limited resources for D2D discovery, the effectiveness of the collision avoidance based schemes is always restricted. Instead, we aim to make the discovery beacon robust against collisions. To achieve this, the cyclic block spreading (CBS) scheme is proposed to spreading the beacon over multiple time slots without widening the bandwidth and the need of redesigning the beacon. That means solely minor modification of specification is required. The simulation and analytic results show that using the CBS direct discovery scheme, the performance in terms of outage probability and successful discovery rate can be significantly improved.

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